Fix the issue of undefined-shift in VP8GetBit.

webrtc/modules/video_coding/utility/vp8_header_parser.cc

Index: webrtc/modules/video_coding/utility/vp8_header_parser.cc
diff --git a/webrtc/modules/video_coding/utility/vp8_header_parser.cc b/webrtc/modules/video_coding/utility/vp8_header_parser.cc
index 631385d0f25095903e676f79dc24e04ea1e1c6cd..ddddfd07aa793d6f5279c5e29c982496272ac93f 100644
--- a/webrtc/modules/video_coding/utility/vp8_header_parser.cc
+++ b/webrtc/modules/video_coding/utility/vp8_header_parser.cc
@@ -35,7 +35,7 @@ static void VP8LoadFinalBytes(VP8BitReader* const br) {
   }
 }
 
-static void VP8LoadNewBytes(VP8BitReader* const br) {
+static bool VP8LoadNewBytes(VP8BitReader* const br) {
   int BITS = 24;
   // Read 'BITS' bits at a time.
   if (br->buf_ + sizeof(uint32_t) <= br->buf_end_) {
@@ -55,6 +55,11 @@ static void VP8LoadNewBytes(VP8BitReader* const br) {
   } else {
     VP8LoadFinalBytes(br);
   }
+  if (br->bits_ < 0) {
+    br->eof_ = 1;

[pbos-webrtc, 2016/04/19 23:11:50]

Actually, does this happen from VP8LoadFinalBytes? or how does this happen? is
eof_ already set and we should just check eof_ from VP8GetBit?

[jackychen_, 2016/04/20 00:27:18]

I'm not sure. So to be safe, I put the check here.

+    return false;
+  }
+  return true;
 }
 
 static void VP8InitBitReader(VP8BitReader* const br,
@@ -73,9 +78,9 @@ static void VP8InitBitReader(VP8BitReader* const br,
 static int VP8GetBit(VP8BitReader* const br, int prob) {
   uint8_t range = br->range_;
   if (br->bits_ < 0) {
-    VP8LoadNewBytes(br);
+    if (!VP8LoadNewBytes(br))
+      return 0;
   }
-
   const int pos = br->bits_;
   const uint8_t split = (range * prob) >> 8;
   const uint8_t value = static_cast<uint8_t>(br->value_ >> pos);